git@vger.kernel.org mailing list mirror (one of many)
 help / color / mirror / code / Atom feed
From: Eric Rannaud <eric.rannaud@gmail.com>
To: Jeff King <peff@peff.net>
Cc: Johannes Schindelin <Johannes.Schindelin@gmx.de>,
	git@vger.kernel.org, Jeremy Serror <jeremy.serror@gmail.com>
Subject: Re: git rebase regression: cannot pass a shell expression directly to --exec
Date: Tue, 16 May 2017 10:21:51 -0700	[thread overview]
Message-ID: <CA+zRj8XLQiTmiVbsJZ7XjdW4bQvMSJpCtKW8xx5JvMKOhBDmLQ@mail.gmail.com> (raw)
In-Reply-To: <CA+zRj8Uxh1SGdVW=zz29Q4m4OnDcs665T0XtV6FiZ_qZSiG-8g@mail.gmail.com>

On Tue, May 16, 2017 at 9:59 AM, Eric Rannaud <eric.rannaud@gmail.com> wrote:
> When I use "git rebase --exec <cmd>" I'm basically writing a "foreach
> commit in range { <cmd> }" in my shell. Same idea with git bisect run.
>
> A transparent optimization that tries execve() then falls back to the
> user's shell sounds like a good idea.

One issue with the execve-else-shell optimization is that sometimes a
binary exists that will shadow an exported function or a shell
builtin:

  git rebase --exec true master^^  # OK but in fact this runs /usr/bin/true

In this case it doesn't really matter. If the optimization is only
applied to "simple commands" (i.e. no arguments), then it's probably
OK. I can't think of problematic cases. Except weird things like:

  $ git rebase --exec time master^
  Executing: time
  Usage: time [-apvV] [-f format] [-o file] [--append] [--verbose]
         [--portability] [--format=format] [--output=file] [--version]
         [--help] command [arg...]
  warning: execution failed: time

/usr/bin/time requires an argument. Even though the bash builtin time
runs fine without argument.

  $ time

  real    0m0.000s
  user    0m0.000s
  sys     0m0.000s

But if the optimization is applied to more complex commands, then we
will have problems. For instance, the builtin echo supports \E, but
/usr/bin/echo doesn't support it.

In any case, the manpage says --exec <cmd> and "<cmd> will be
interpreted as one or more shell commands.", it doesn't say "--exec
<executable>".

  parent reply	other threads:[~2017-05-16 17:21 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-15 18:08 git rebase regression: cannot pass a shell expression directly to --exec Eric Rannaud
2017-05-16  3:25 ` Jeff King
2017-05-16  3:37   ` Jeff King
2017-05-16 16:41     ` Jonathan Nieder
2017-05-16 16:47       ` Jeff King
2017-05-16 17:11         ` Eric Rannaud
2017-05-16 17:15         ` Brandon Williams
2017-05-16 17:23           ` Jeff King
2017-05-16 17:30             ` Brandon Williams
2017-05-16 19:14             ` Linus Torvalds
2017-05-16 19:35               ` [TANGENT] run-command: use vfork instead of fork Eric Wong
2017-05-16 20:47                 ` Linus Torvalds
2017-05-16 21:11                   ` Brandon Williams
2017-05-16 20:12               ` git rebase regression: cannot pass a shell expression directly to --exec Johannes Schindelin
2017-05-16 20:27                 ` Linus Torvalds
2017-05-16 17:37         ` Jonathan Nieder
2017-05-16  3:40   ` Junio C Hamano
2017-05-16  3:53     ` Jeff King
2017-05-16  4:08       ` Jeff King
2017-05-16 16:45       ` Eric Rannaud
2017-05-16 10:46     ` Johannes Schindelin
2017-05-16 10:23 ` Johannes Schindelin
2017-05-16 16:18   ` Jeff King
2017-05-16 16:59     ` Eric Rannaud
2017-05-16 17:14       ` Kevin Daudt
2017-05-16 17:29         ` Eric Rannaud
2017-05-16 17:41           ` Jeff King
2017-05-16 17:21       ` Eric Rannaud [this message]
2017-05-16 17:37         ` Jeff King

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://vger.kernel.org/majordomo-info.html

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CA+zRj8XLQiTmiVbsJZ7XjdW4bQvMSJpCtKW8xx5JvMKOhBDmLQ@mail.gmail.com \
    --to=eric.rannaud@gmail.com \
    --cc=Johannes.Schindelin@gmx.de \
    --cc=git@vger.kernel.org \
    --cc=jeremy.serror@gmail.com \
    --cc=peff@peff.net \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this public inbox

	https://80x24.org/mirrors/git.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).